Applications in medicine, science, and engineering commonly use microscopy to determine information about a given sample. Such applications likewise exploit spectroscopic information when analyzing a sample. In particular, the optical response of a sample often depends on the spectral content of light illuminating the sample, and that spectral dependence provides additional information about the sample or components therein. Not surprisingly, it is often desirable to obtain both spatial and spectral information about a sample to more accurately identify or characterize different regions or components of the sample. For example, one may want to spatially resolve the optical response of a sample (e.g., the optical transmission) as a function of illumination light at a particular wavelength or superposition of wavelengths. Furthermore, the image of a sample at a particular wavelength or superposition of wavelengths may be useful in distinguishing and spatially isolating one component of the sample from other components of the sample.
In such applications, however, it is important that light intensity variations in the detected image can be properly associated with the sample. Accordingly, variations in the relative spectral content of the illumination light across its spatial profile should be minimized or carefully calibrated. Furthermore, any spectroscopic imaging system should provide robust and reliable performance, and efficiently exploit the available illumination light.
The invention features a multi-spectral microscopy system for illuminating a sample with light of a selectable spectral content and generating an image of the sample in response to the illumination. The selection of the spectral content of the illumination and the image detection can be performed through an electronic control system. The multi-spectral microscopy system includes a multispectral illuminator that provides output radiation having the selectable spectral content. A preferred set of optical arrangements for the multispectral illuminator generates the output radiation so that the spectral content of the output radiation is substantially uniform across its transverse profile. In particular, the absolute intensity of the output radiation may vary across its transverse profile, but the relative spectral content of the radiation is substantially uniform across the transverse profile. Furthermore, the multispectral illuminator can include monitoring optics and a corresponding detector array that independently monitors the output in each spectral band of the radiation produced by the multispectral illuminator. The monitoring provides calibration, feedback, and/or source aging information to insure robust and reliable performance for the multispectral illuminator. The multi-spectral microscopy system also includes a microscope which illuminates the sample with light derived from the output of the multispectral illuminator, and beam modification optics, which modify the output from the lamp prior to the microscope to increase the light efficiency of the microscope and fully exploit field of view and resolution of the microscope. In preferred embodiments, the beam modifications optics provide independent and selectable control over the spot size and divergence cone of the illumination pattern on the sample.
We will now summarize different aspects, features, and advantages of the invention.
In general, in one aspect, the invention features a multispectral illuminator for providing EM radiation with a selectable frequency content. The multispectral illuminator includes: a dispersive element which during operation provides an angular dispersion for incident EM radiation; a light source array including an array of light sources providing EM radiation at different wavelengths; and an optical system having an optical power. The optical system is positioned relative to the source array and the dispersive element to image the dispersive element at infinity with respect to the light source array for at least one of the different wavelengths in a paraxial approximation. The position of each light source along the array and the angular dispersion of the dispersive element are selected to cause at least a portion of the EM radiation from the source array incident on the dispersive element through the optical system to propagate along a common direction.
Embodiments of the multispectral illuminator may include any of the following features.
The optical system can include any of a singlet lens, a composite lens system, and one or more curved reflective surfaces.
During operation, the optical system may collimate the EM radiation emerging from each light source within a preset cone angle and direct the collimated radiation from each light source to be coextensive on the diffractive element.
The optical system can define a focal length for at least one of the different wavelengths, and the light source array and the diffractive element can be each spaced from the optical system by a distance substantially equal to the focal length.
The spatial extent of the dispersive element can define an aperture stop for the optical system. For example, the dispersive element can include an iris for varying the spatial extent of the dispersive element.
The optical system and the dispersive element can cause the EM radiation propagating along the common direction to have a spatial distribution that is substantially wavelength independent.
The common direction can be substantially collinear with a chief ray from a central one of the light sources.
The dispersive element can be a reflective dispersive element (e.g., a reflective grating). For example, the reflective dispersive element can direct the radiation back to the optical system along the common direction, and the optical system can focus the radiation received from the reflective dispersive element to a spot in an image field. The image field may be substantially coplanar with a plane defined by the source array. Also, the common direction may be substantially perpendicular to a plane defined by the source array. The source array may include a substrate supporting the light sources, and the spot in the image field may coincide with an aperture in the substrate. The light sources may extend along an axis, and the aperture can lie along the light source axis. Alternatively, the aperture can lie above or below the light source axis. The optical system may form a telecentric imaging system based on the reflection by the dispersive element. The multispectral illuminator may further include an optical fiber positioned to receive the focused radiation from the aperture in the substrate.
Alternatively, the dispersive element may be a transmissive dispersive element (e.g., a transmission grating). The multispectral illuminator may further include a second optical system position to receive the radiation from the transmissive dispersive element propagating along the common direction and focus that radiation to a spot in an image field. The common direction may be substantially perpendicular to a plane defined by the source array. The two optical systems may form a telecentric imaging system.
The second optical system may define a focal length, and the transmissive dispersive element and the image field can be each spaced from the second optical system by a distance substantially equal to the focal length of the second optical system. The multispectral illuminator may further include an optical fiber positioned to receive the focused radiation from the spot in the image field.
The multispectral illuminator can further include an electronic controller coupled to the array of light source for selectively adjusting the EM radiation provided by each light source.
The EM radiation provided by the array of light sources may span wavelengths within the range of 400 nm to 1000 nm.
The source array may includes a substrate supporting the light sources, and each light source may include at least one light emitting diode (LED) mounted on the substrate. For example, each light source may include multiple light emitting diodes (LED) mounted on the substrate.
The source array may include a substrate supporting the light sources, and the substrate may further support a reflective cup surrounding each light source to enhance light emission from the light sources in a forward direction.
The light source array may further include a lenslet array aligned with the array of light sources.
The source array can support at least two of the light sources at different axial positions relative to the optical system to reduce at least one of field curvature and axial chromatic aberration in the collimated EM radiation incident on the dispersive element. For example, the substrate can have curved surface supporting the light sources to provide the different axial positions.
Furthermore, the source array can support at least two of the light sources at lateral positions along the array that reduce at least one of distortion and lateral chromatic aberration in the collimated EM radiation incident on the dispersive element. For example, the substrate can support the light sources at lateral positions along the array that vary nonlinearly with the central frequency of the EM radiation provided by each light source.
The multispectral illuminator may further include beam modification optics positioned to receive light derived the EM radiation propagating along the common direction and produce an illumination pattern having a desired spot size and a desired divergence cone across the spot size. The beam modification optics may include a diffuser (e.g., a holographic diffuser) for modifying the divergence of an incident beam. Moreover, the beam modification optics may include multiple diffusers each providing a different scattering cone, where each of the multiple diffusers can be selectably positioned to intercept the light derived from the EM radiation propagating along the common direction. The beam modification optics can further include at least one lens. Moreover, the beam modification optics may further include multiple lenses having different focal lengths, where each of the multiple lenses can be selectably positioned to intercept the light derived from the EM radiation propagating along the common direction.
The multispectral illuminator may further include a detector positioned to receive a monitoring beam derived from a portion the EM radiation propagating along the common direction.
The multispectral illuminator may further include a multi-channel detector positioned to receive an array of monitoring beams derived from the EM radiation provided by the source array, wherein each monitoring beam corresponds to one of the light sources. In some embodiments, the multi-channel detector can be positioned above or below the array of sources. For example, a substrate in the source array can further support the multi-channel detector.
To produce the monitoring beams, the multispectral illuminator may include a monitoring beam optic positioned between the source array and the optical system for producing the monitoring beams from corresponding portions of the EM radiation provided by the light sources. For example, the monitoring beam optic can include a partially transparent roof mirror extending parallel to the array of light sources.
In other embodiments, the dispersive element can cause a first portion of the incident EM radiation from the light sources to propagate along the common direction and cause a second portion of the incident EM radiation to form the monitoring beams. For example, the dispersive element may reflect or transmit the second portion to form the monitoring beams.
Furthermore, the dispersive element may diffract the first portion to cause it to propagate along the common direction and diffract the second portion along an order different from that of the first portion to form the monitoring beams. The monitoring beams produced by the dispersive element may propagate through the optical system prior to being received by the multi-channel detector.
In yet further embodiments, the multispectral illuminator includes a monitoring beam optic positioned between the optical system and the dispersive element to produce the monitoring beams from a portion of the EM radiation being imaged by the optical system. The monitoring beams may propagate through the optical system prior to being received by the multi-channel detector. For example, the monitoring beam optic may be a wedge positioned immediately adjacent the dispersive element.
The multispectral illuminator may be part of a spectral imaging system that further includes: beam delivery optics positioned to form an illumination pattern on a sample based on the EM radiation produced by the multispectral illuminator; an detection optics (e.g., a lens) positioned to receive light from the sample in response to the illumination pattern and form an image of the sample in a focal plane; and an imaging detector located in the focal plane for detecting and spatially resolving the image of the sample.
The beam delivery optics in the spectral imaging system may include a diffuser (e.g., a holographic diffuser) for controlling the divergence of an incident beam. Moreover, the beam delivery optics may include multiple diffusers each providing a different scattering cone, and each of the multiple diffusers can be selectably positioned to intercept EM radiation used to form the illumination pattern. Also, the beam delivery optics may further include at least one lens. Moreover, the beam delivery optics may further include multiple lenses having different focal lengths, and each of the multiple lenses can be selectably positioned to intercept the light derived from the EM radiation used to form the illumination pattern. The detection optics collect light within a numerical aperture, and the beam delivery optics may be selected to cause the EM radiation in the illumination pattern incident on the sample to fill the numerical aperture of the detection optics. Furthermore, the detection optics collect light from the sample over a sample area for light rays emerging from the sample area within the numerical aperture, and the beam delivery optics may be selected to cause the illumination pattern to fill the sample area and the numerical aperture.
In general, in another aspect, the invention features a multispectral illuminator for providing EM radiation with a selectable frequency content. The multispectral illuminator includes: a dispersive element which during operation provides an angular dispersion for incident EM radiation; a light source array including an array of light sources providing EM radiation at different wavelengths; and an optical system having an optical power. During operation, the optical system collimates the EM radiation emerging from each light source within a preset cone angle and directs the collimated radiation from each light source to be coextensive on the diffractive element, and the position of each light source along the array and the angular dispersion of the dispersive element are selected to cause at least a portion of the EM radiation from the source array incident on the dispersive element through the optical system to propagate along a common direction.
In general, in another aspect, the invention features a multispectral illuminator for providing EM radiation with a selectable frequency content. The multispectral illuminator includes: a dispersive element which during operation provides an angular dispersion for incident EM radiation; a light source array including an array of light sources providing EM radiation at different wavelengths; and an optical system having an optical power. The optical system defines a focal length for at least one of the different wavelengths, the light source array and the diffractive element are each spaced from the optical system by a distance substantially equal to the focal length, and the position of each light source along the array and the angular dispersion of the dispersive element are selected to cause at least a portion of the EM radiation from the source array incident on the dispersive element through the optical system to propagate along a common direction.
In general, in another aspect, the invention features a multispectral illuminator for providing EM radiation with a selectable frequency content. The multispectral illuminator includes: a dispersive element which during operation provides an angular dispersion for incident EM radiation; a light source array including a substrate supporting an array of light sources providing EM radiation at different wavelengths; and an optical system having an optical power. The optical system is positioned to direct light from the light source array to the dispersive element, and the position of each light source along the array and the angular dispersion of the dispersive element are selected to cause EM radiation from the source array incident on the diffractive element through the optical system to propagate along a common direction. The substrate supports at least two of the light sources at different axial positions relative to the optical system to reduce at least one of field curvature and axial chromatic aberration in the collimated EM radiation incident on the dispersive element.
In general, in another aspect, the invention features a multispectral illuminator for providing EM radiation with a selectable frequency content. The multispectral illuminator includes: a dispersive element which during operation provides an angular dispersion for incident EM radiation; a light source array including an array of light sources providing EM radiation at different wavelengths; an optical system having an optical power, and a multi-channel detector positioned to receive an array of monitoring beams derived from the EM radiation provided by the source array. The optical system is positioned to direct light from the light source array to the dispersive element. Each monitoring beam corresponds to one of the light sources. The position of each light source along the array and the angular dispersion of the dispersive element are selected to cause EM radiation from the source array incident on the diffractive element through the optical system to propagate along a common direction.
Embodiments of the multispectral illuminator may include any of the following features.
The multi-channel detector may be positioned above or below the array of sources. For example, a substrate in the source array can support the multi-channel detector.
To produce the monitoring beams, the multispectral illuminator may further include a monitoring beam optic positioned between the source array and the optical system for producing the monitoring beams from corresponding portions of the EM radiation provided by the light sources.
In other embodiments, the dispersive element may cause the first portion of the incident EM radiation from the light sources to propagate along the common direction, and cause a second portion of the incident EM radiation to form the monitoring beams. For example, the dispersive element may reflect or transmit the second portion to form the monitoring beams. Furthermore, the dispersive element may diffract the first portion to cause it to propagate along the common direction, and diffract the second portion along an order different from that of the first portion to form the monitoring beams. The monitoring beams may then propagate through the optical system prior to being received by the multi-channel detector.
In yet further embodiments, the multispectral illuminator may further include a monitoring beam optic positioned between the optical system and the dispersive element to produce the monitoring beams from a portion of the EM radiation being directed by the optical system. The monitoring beams may then propagate through the optical system prior to being received by the multi-channel detector. The monitoring beam optic may be a wedge positioned immediately adjacent the dispersive element. The multi-channel detector may then be positioned above or below the array of sources, and the optical system directs the monitoring beams from the monitoring beam optic to form an image of the source array on the multi-channel detector. A substrate in the source array may be used to support the multi-channel detector.
The multispectral illuminator may also be part of a spectral imaging system that further includes: beam delivery optics positioned to form an illumination pattern on a sample based on the EM radiation produced by the multispectral illuminator; detection optics position to receive light from the sample in response to the illumination pattern and form an image of the sample in a focal plane; and an imaging detector located in the focal plane for detecting and spatially resolving the image of the sample.
In general, in another aspect, the invention features a spectral imaging system including: a multispectral illuminator producing EM radiation, the illuminator including an array of sources at different wavelengths; beam modification optics positioned to form an illumination pattern on a sample based on the EM radiation produced by the multispectral illuminator; detection optics (e.g., a lens) positioned to receive light from the sample in response to the illumination pattern and form an image of the sample in a focal plane; and an imaging detector located in the focal plane for detecting and spatially resolving the image of the sample. The illumination pattern formed by the beam modification optics produce a desired spot size and a desired divergence cone across the spot size. The beam modification optics include a diffuser (e.g., a holographic diffuser) for controlling at least one of the spot size and divergence cone of the illumination pattern.
Embodiments of the spectral imaging system may include any of the following features.
The EM radiation produced by the multispectral illuminator may have a substantially spectrally uniform spatial profile.
The beam modification optics may include multiple diffusers each providing a different scattering cone and wherein each of the multiple diffusers can be selectably positioned to intercept EM radiation used to form the illumination pattern.
The beam modification optics may further include at least one lens. Furthermore, the beam modification optics further include multiple lenses having different focal lengths and each of the multiple lenses can be selectably positioned to intercept the light derived from the EM radiation used to form the illumination pattern.
The detection optics collect light within a numerical aperture, and the beam delivery optics may be selected to cause the EM radiation in the illumination pattern incident on the sample to fill the numerical aperture of the detection optics. Furthermore, the detection optics collect light from the sample over a sample area for light rays emerging from the sample area within the numerical aperture, and the beam delivery optics may be selected cause the illumination pattern to fill the sample area and the numerical aperture.
Other features, objects, and advantages of the invention will be apparent from the following detailed description.